Ultrafast sonochemistry-based approach to coat TiO₂ commercial particles for sunscreen formulation

TiO₂ is a common inorganic filter used in sunscreens due to its photoprotective effect on the skin against UV radiation. However, the use of this kind of material in cosmetics is limited by its inherent photocatalytic activity. It is known that coating on TiO₂ surface can improve some features. Although, many of the methodologies used for this purpose are still laborious and time-consuming. Thus, this work reports a novel, easy, cheap and fast strategy to coat TiO₂ particles by using a sonochemistry approach, aiming to decrease photocatalytic activity and to enhance colloidal stability. For this proposal, SiO₂, Al₂O₃, ZrO₂ and sodium polyacrylate (PAANa) were used to tune the surface of commercial TiO₂ particles and they were applied in a sunscreen formulation. The samples were characterized by XRPD, FT-IR, DLS, EDS, SEM and TEM. The photocatalytic activity and UV-shielding ability were also evaluated. The sunscreen formulations were prepared and characterized by zeta potential, DLS, and Sun Protection Factor (SPF). FT-IR, EDS, and charge surface of the particles confirmed the success of the sonochemistry coating. Additionally, TiO₂@Al₂O₃, TiO₂@SiO₂ and TiO₂@PAANa show a lower photocatalytic activity than original TiO₂ with similar UV-shielding ability. The sunscreens produced with the coated TiO₂ have similar SPF to the one with commercial TiO₂. Specifically, the sunscreen with TiO₂@PAANa shows an increase in colloidal stability. Herein, the incorporation of the sonochemical-coated TiO₂ particles in sunscreen formulations may produce sunscreens with better aesthetic appearance and a greater health security due to its lower free radicals production.